The CDC analyzed three years of data from the National Survey of Family Growth, which gathers information on factors including pregnancy, use of birth control and men’s and women’s health.

Scientists estimate 3.3 million women in the U.S. are at risk of exposing their developing babies to alcohol.

"Alcohol can harm a developing baby before a woman knows she is pregnant,” said CDC Principal Deputy Director Anne Schuchat. “About half of all pregnancies in the United States are unplanned, and even if planned, most women won’t know they are pregnant for the first month or so when they might still be drinking. The risk is real. Why take the chance?"

Women typically learn they’re pregnant about four to six weeks after conception, according to the CDC. Even within those first few weeks, mothers can cause “lasting physical, behavioral and intellectual disabilities that can last for a child’s lifetime,” health officials said.

“There is no known safe amount of alcohol – even beer or wine – that is safe for a woman to drink at any stage of pregnancy,” the CDC added.

The agency released the following recommendations for women:

Talk with their healthcare provider about their plans for pregnancy, their alcohol use, and ways to prevent pregnancy if they are not planning to get pregnant.

Stop drinking alcohol if they are trying to get pregnant or could get pregnant.

Ask their partner, family and friends to support their choice not to drink during pregnancy or while trying to get pregnant.

Ask their healthcare provider or another trusted person about resources for help if they cannot stop drinking on their own.